In the hydrometallurgical industry, it is of common practice to refine metal by electrolysis in electrolytic cells especially designed for this purpose. The metals to be refined are usually conventional metals such as copper, zinc, nickel or cadmium, or precious metals such as silver, platinum or gold, and others.
It is also of common practice to use metal plates as anodes or cathodes or both. These metal plates often weight several hundred pounds. Usually, the metal to be refined, or the metal used to carry the electric current, is in the form of plates of a given thickness, which are provided at their upper end with two laterally extending projections, called hanging legs. Such projections facilitate gripping, handling and hanging of the plates on lateral sidewalls of the cells. These projections also serve to electrically contact or insulate the electrode.
In use, the electrode plates which, as mentioned, can each weigh several hundred pounds, are immersed into the cells in parallel relationship and are used as anodes, cathodes or both, depending on the affinity of the metal being refined.
In order to have the electrodes positioned in a precise desired location, it is of common practice to place a component called a “capping board” or a “bus bar insulator” onto the top surface of each lateral sidewall of the cells. These capping boards are used to position the plates with respect to each other. They are also used as electric insulators between adjacent cells and/or the electrodes and/or the ground.
In practice, the capping boards are used not only as supports to position the electrodes, but also as supports to avoid damage to the masonry, concrete or polymer-concrete forming the lateral side walls of the cells during the insertion and removal of the heaving electrodes. They are also used for electrolytic refining and electrowinning of metals.
Insulating capping boards are used to hold the electrodes at very precise positions. They are also used in combination with electrically conductive “contact bars” the purpose of which is to allow electrical connection between the ends of the anodes and cathodes located in adjacent cells. Thus, the combined use of capping boards and contact bars allows both insulation and distribution of electric current.
To achieve proper electrical contact with the contact bar, the plates forming the electrodes are provided with support hanging legs externally projecting on their opposite upper ends. Only one end of the legs of each plate is in contact with a contact bar on one side of the cell where it is located. The other leg of the same plate is held onto the capping board located on the opposite side of the cell in such a way as to be insulated. Thus, the capping board per se plays the role of an insulator and is thus made of insulating material. The contact bar usually extends over the full length of the corresponding capping board in order to connect altogether all the anodes of one cell to all the cathodes of the adjacent cell and vice versa. The contact bar may interconnect all of the cathodes to the anodes on other adjacent cells or perform other electric connection function between electrodes as desired.
In hydrometallurgical refining of metals, there are two main configurations that may be used to support the electrodes: symmetrical configurations using symmetrical anodes and cathodes and asymmetrical configurations using asymmetrical anodes and cathodes. The capping boards and contact bars are provided depending on the type of electrodes to be used. Thus, different capping board and contact bar systems will be used for symmetrical and asymmetrical electrodes.
The electrolytic system using symmetrical electrodes uses an assembly of three different components. Referring to FIG. 1 (Prior Art), there is a first insulator 10 referred to as a “bus bar insulator”, a machined dog bone contact bar 12 and a second insulator 14 referred to as a “coronary insulator”. FIG. 2 (Prior Art) shows a perspective view of part of the machined dog bone contact bar 12. Symmetrical support systems are practical and require low level of monitoring since for the electric positioning either side of the electrodes can be used and interchanged because the hanging bars are symmetrical. However, it is inconvenient and expensive to require two insulators 10 and 14 as well as a contact bar that is rather large and thus expensive. In addition, in such known symmetrical systems, copper (or other metals) sulphate and acid mist called “sulphatation” may occur between the two insulators, which corrodes the contact bar and allows passage of electric current. Such current leakage creates significant efficiency losses and the acid mist sulphatation also results in a lower quality of refined metal such as copper and reduced overall efficiency of the refining process.
Another disadvantage is that when the contact bar or coronary insulator breaks or become unusable, replacement is very complicated, difficult and time consuming. The electrolytic system using asymmetrical electrodes uses an assembly of two different components. Referring to FIG. 3 (Prior Art), there is a contact bar 16 laying on a insulating capping board 18 having two rows of alternating staggered or “offset” insulating seats 20 in between which the contact bar 16 sits. Asymmetrical support systems require a great deal of monitoring since inverse positioning of the anodes or cathodes can cause significant problems and damage. Monitoring is thus a significant expense. Errors in installation inadvertently inversing the orientation of the electrodes is problematic and dangerous because it can cause, for example, major short circuits requiring production downtime, and can create or induce fire, making their use more onerous and dangerous.
In addition, by way of further background in the field of capping boards and/or contact bars, the following patent documents U.S. Pat. Nos. 5,645,701, 7,204,919, U.S. Ser. No. 12/528,435, U.S. Pat. No. 7,223,324 and U.S. Ser. No. 12/524,852, are hereby incorporated herein by reference.
There is indeed a need in the industry for a technology that would overcome at least some of the aforementioned disadvantages and challenges.